In the past the range accuracy and receiver sensitivity of laser range finders has been measured by methods such as aiming the device at a plurality of targets at different ranges set up on a test range. Such a testing method requires much space, is subject to errors caused by differing atmospheric conditions, and requires an accurate measurement of the range of the different targets, which can be time consuming. Another method which has been used is to apply the laser pulse output of the device being tested to a coiled length of optical fiber and to feed the output of the optical fiber to the device's receiver. The range reading obtained from such a device will be considerably more than that from a target at half the distance of the optical fiber's length, since the speed of propagation of the laser beam in the fiber is less than that "in vacuuo" by a factor equal to the index of refraction of the fiber. Thus an accurate knowledge of the index of refraction of the fiber is necessary if this method is to be accurate, and this is not always known with the required accuracy.
The present invention overcomes many of the disadvantages of these prior art testing and calibration techniques by utilizing one range finder as a testing device for another range finder, and interconnecting the two devices with certain readily available electronic measuring devices to obtain accurate range and sensitivity calibration in the laboratory.